The Black Cats have lost eight of their 10 Premier League encounters since Bent departed in a £24million move back in January.
Darren Bent: "Of course I feel sympathy for them. I had good times there. I never want to see them struggle and do badly so hopefully they'll turn it around.
"It's disappointing to see them doing badly but, at the same time, as much as I'd like them to do well, I'd like Aston Villa to do even better.
"All I can do is keep concentrating on Aston Villa."